THERMOCOAX Space Products Catalyst Bed Heaters – Cartridge Design Spacecraft Propulsion

Thermocoax Pedigree

THERMOCOAX has been a worldwide key player for 15 years the design, development and manufacture of heating systems for the space market.

We are providing solutions for :

Ground applications :

  • R&D programs with institutes
  • Ground equipment

Flying models :

  • Heating management system on Satcom
  • Catalyst bed heater for chemical propulsion
  • Heating solution for Hall effect thruster

Scientific Mission :

  • Heating system on Curiosity rover
  • Heating Element on ISS for MSL
  • Heating Element for pyrolyser on the Cassini-Huygens Titan probe



Technical Applications of Catalyst Bed Heaters

Monopropellant Thruster is a small rocket engine used for attitude, trajectory and orbit control of satellites and spacecraft.

The main reason for catalyst bed heaters on monopropellant thrusters is to improve the performance at startup.

Typically, when the catalyst is cold, the first pulse is weak and has large delays from the valve to the centroid of the thrust.

Using a heating component is a strategic solution to avoid unstable performance when the thruster is used for infrequent attitude control pulsing, as the bed could potentially cool down between pulses.


With regard to Space Debris Mitigation (SDM), technical modifications will be implemented on new satellite platforms.

Through the CleanSat program, the ESA supports LEO Platforms for compliance with the SDM requirements.

This is an opportunity for THERMOCOAX to contribute to this program with catalyst bed heaters on propulsive de-orbiting. The objective is to perform the maneuver for the different classes of spacecraft with mass ranges from below 10kg, up to 2000kg.

Then the spacecraft is expected to be completely destroyed during the atmospheric re-entry with a negligible risk for ground populations.


Technical Description of Catalyst Bed Heater

The heating cartridge is the design most used over the last 20 years.

The heating cartridge works continually to keep the catalyst bed no lower than a certain value to get a more efficient start up when the thruster is activated.

For de-orbiting, we can consider the use of the 400 Newton apogee motor which was unused for the whole life of the spacecraft. When the de-orbiting maneuver is decided, the oversized catalyst bed heater has the task of pre-heating the dormant catalyst bed for its last thrust.


Catalyst Bed Heater Cartridge :

  • 2 redundant electrical circuits
  • Rated power supply: 28 Volt to 40 Volt
  • Type of power for each circuit:
    • 2 Watt at 28 V DC
    • 8 Watt at 28 V DC
    • 12 Watt at 32 V DC
  • 70 W/cm²
  • Nickel chromium wires
  • Ceramic insulator
  • Inconel 600
  • Overvoltage 42 V DC

Capture bis

Mineral-Insulated Cable :

  • Inconel 600 sheath
  • 4 wire nickel chromium
  • Dielectric 500 Volt
  • Ø2.3 down to 1mm
  • Bending radius 3*Ø


Lead Wires :

  • 4 wires
  • Color code for each loop
  • AWG24 or 26
  • Strength 1.4 kg


Acceptance test criteria of the catalyst bed heater :

  • Helium leak test
  • X-Ray of the heating cartridge
  • X-Ray of the MIC/lead wires junction
  • Lead attachment strength test
  • Visual and mechanical inspection
  • Overvoltage
  • Line Resistance
  • Insulation Resistance under 500 Volts
  • Burn-in test
  • Dielectric 100/300/500V AC, 60Hz/60s
  • Weight
  • Final manufacturing report

Response Time :

  • With only one circuit: 3.2 Watt
  • Heating cartridge painted black
  • Measured with IR camera


  • Measure with thermocouples
  • One circuit of 3.2 Watt


Results :

  • Input voltage: 28 V DC
  • Power :
    • Min: 3.02 W with R=230Ω
    • Nominal : 3.2 W with R=245Ω
    • Max: 3.41 W with R=260Ω
  • Power density : 0.70 Watt/cm²


Test List for Qualification Program of the Catalyst Bed Heater

Thermocoax drives and conducts the qualification test program in accordance with our customer’s specification.

Our engineers write the QTP for customer approval prior to running the test.

Most of the tests on the catalyst bed heater are performed in THERMOCOAX’s test laboratories (thermal, humidity, electrical etc.). Those requiring heavy equipment (vibration, acceleration, shocks  etc.) are subcontracted to external laboratories or conducted by our customers with the complete propulsion system.

-Typical qualification Test  list on catalyst bed heater :

  • Vibration
  • Acceleration
  • Mechanical shock
  • Pyrotechnic shock
  • Helium leak test
  • Burn-in test
  • Humidity test
  • Hot firing test
  • Electrical cycling test
  • Thermal cycling test
  • Lead attachment test
  • Dielectric test
  • Destructive physical analysis
  • X-ray examination



Packaging and Cleanliness :

  • THERMOCOAX is focusing on high quality catalyst bed heater products for the best stability and repeatability in operation. We have understood  our customers’ challenges to manufacture spacecraft for 15 years and to improve human life.

In THERMOCOAX’s we are working hard to participate in these incredible challenging programs


Specific packaging is organized to ensure excellent condition of the catalyst bed heater during transportation and storage :


THERMOCOAX has supplied many programs on 1, 5, 20, 200 and 400 Newton hydrazine thrusters, here are a few example s:

  • Sentinel
  • Pleaiades
  • Myriad
  • Alsat
  • Elisa
  • SSOT
  • Jason
  • Taranis
  • Syracuse
  • Sicral
  • Proteus
  • Giove

THERMOCOAX is the major player for catalyst bed heaters and is proud to participate in great space programs.